asterisk users - May 2004 - Problem with digits blending on inbound puls ed digits?

To answer my own question for the record:

The relevant timing parameters in zaptel.h are 

 #define ZT_MINPULSETIME (15 * 8)        /* 15 ms minimum */
 #define ZT_MAXPULSETIME (100 * 8)       /* 150 ms maximum default, lowered
to 100ms */
 #define ZT_PULSETIMEOUT ((ZT_MAXPULSETIME / 8) + 50)

And the pulse detecion loop that consumes these parameters begins at line
4866 of zaptel.c  

The intermittant loss of pulses from second and/or subsequent digits
appeared to be caused by a slightly too long blanking period that occurs
after the interdigit timeout occurs. Lowering MAXPULSETIMEOUT, recompiling
and reloading the zaptel.o modules appears to have fixed the problem. Likely
this is happening because they are CO generated DID pulses and hence tuned
for as fast a signalling rate as possible.

For the interested (or bored) far too much information about digit
signalling can be gleaned from:

http://ftp.tiaonline.org/tr-41/tr4138/Public/2004-02-Vancouver/TR41.3.8-04-0
2-002-L-(word)PN-3-4350.230RV3-Draft02-NetworkSignaling%20,DMcKinnon,AST.doc

-----Original Message-----
From: Kris Boutilier [mailto:Kris.Boutilier@scrd.bc.ca]
Sent: May 28, 2004 2:50 PM
To: asterisk-users@lists.digium.com
Subject: [Asterisk-Users] Problem with digits blending on inbound pulsed
digits?


I have a situation where I am receiving DID calls using Immediate Start
Pulse signalling on a Loop Start trunk. The line terminates on a Newbridge
Mainstreet 3624 channel bank, which provides battery etc. The channel is
converted and routed to Asterisk. The lines are configured as follows:

{clip}

Now, the first problem I had was with the first few pulses getting clipped
from the inbound digits. Setting 'debounce=50' resolved that. My current
problem is 'blending' of digits. For example, if I receive pulses for 8
0 1
or  8 0 8 they are correctly recognised almost all of the time. If however I
receive 8 8 8 they are almost never correctly translated. Essentially, it
seems to be something to do with timing for the interdigit gap. I have tried
terminating the lines on a Norstar MICS DID card w/Immediate Pulse and all
digits are correctly received all the time.

{clip}